This invention relates to printing machines of the silk screen type. Such machines are well-known for use in the printing of surfaces of objects of various character.
Silk screen printing machines involve the use of a printing fluid which is transferred to the surfaces of objects through a stencil screen made of silk or other suitable fabric. A squeegee is used in conjunction with the screen for forcing the ink through the screen openings.
In the operation of the machines, it is necessary to provide means for moving the object, screen and squeegee relative to each other. For example, when printing a flat, continuous surface, the screen is held in engagement with the surface, and the squeegee is moved across the screen. When printing cylindrical or oval surfaces, the object may be rotated about an axis with the screen being moved in synchronism with the rotation. In this case, the squeegee will be held stationary for achieving the ink transfer function.
In addition to the movements necessary during the printing operation, the screen and squeegee are typically moved away from the printing position after an object is printed. This permits removal of the object printed and the location of an unprinted object at the printing position. The screen and squeegee are then moved back into position for the next printing operation.
When moving the screen and squeegee away from the printing position, it is usually also necessary to move the squeegee out of contact with the screen particularly where the relative squeegee and screen positions are adjusted at the end of each printing cycle. This avoids problems with the quality of printing which would occur if the squeegee contacted the screen except during the printing operation.
Dubuit Pat. No. 3,090,300 illustrates a construction for supporting a screen and squeegee in a silk screen printing machine. In this construction, parallel spaced shafts and linkage means provide support for the screen and squeegee. One of the shafts has supporting links keyed thereto, at least one link being connected to the squeegee and separate link means connected to the screen whereby rotation of the shaft drives the links for movement of the squeegee and screen. The squeegee pivots away from the screen as the screen is moved away from an object after completion of a printing operation whereby the squeegee is out of contact with the screen at this time.
Another system for moving the squeegee and screen supports is set forth in British Pat. No. 984,204. In this instance, separate fluid-operated rams are connected to the screen and squeegee. These rams are actuated at appropriate intervals for controlling the relative movements of this structure during and between printing operations.